Silica-thickened grease containing acid amide dispersant



ates

United This invention relates to new and useful improvements in grease compositions,'and more particularly to a silicathickened grease utilizing an improved dispersant for the silica gelling agent.

This invention is based upon our discovery that acid amides are superior dispersants for silica-thickened greases. This invention is further based upon our discovery that certain of the acid amides are not only useful as dispersants for silica-thickened greases but are also water-proofing agents which resist destruction of the grease upon contact with water.

Although the classical definition of lubricating greases is restricted to oils which are thickened or gelled with soaps, there has been developed a number of grease-like lubricants which are based upon synthetic lubricating liquids other than oil, or which utilize gelling or thickening agentsother than soaps, but which are recognized as greases. In fact, non-soap-thickened greases have been given considerable attention in recent years for high temperature applications, since these greases do not melt at elevated temperatures. These greases are discussed at considerable length in Manufacture and Application of Lubricating Greases, Boner, Reinhold (1954). The non-soap-thickened greases differ very substantially from the soap-thickened greases and differ among themselves to a very great extent. For example, the non-soap-thickened greases generally are less susceptible to bleeding and to change of consistency on increase of temperature. Bentone greases are thermally stable and mildly resistant to water. On the other hand, silica-thickened greases are thermally stable but decompose readily upon contact with water unless waterproofing agents are used to prevent separation of the silica particles from the oil. Additives which are used for various purposes in connection with the soap-thickened greases are quite variable in their efiect on the various non-soap-thickened greases. For example, metal carbamates and thiocarbamates which are reported (in US. Patents 2,652,362 and 2,652,363) to be useful as corrosion inhibitors and stabilizers for soap-thickened greases are completely ineffective as stabilizers or dispersants for bentone and silica-thickened greases. Butyl stearate and coconut oil are each reported (in US. Patent 2,662,058) to be useful as dispersion aids for bentone greases but have been found to be completely ineffective as dispersants for silica-thickened greases. These variations in the effect of stabilizers and dispersants for soap-thickened and non-soap-thickened greases indicate the highly empirical nature of the greasemaking art in general and the art of making non-soapthickened greases in particular.

It is therefore one object of this invention to provide a new and improved silica-thickened grease of high yield.

Another object of this invention is to provide a newand improved silica-thickened grease containing a dispersant for the silica which also prevents decomposition of the grease upon contact with water.

A feature of this invention is the provision of an improved silica-thickened grease which utilizes oil-soluble acid amides as dispersants.

" Another feature of this invention is the provision of an improved silica-thickened grease which utilizes oi1- l1 V I oil-soluble acid amide of the formula 0 R2 Rr-l iN Rf where R R and'R are of the group consisting of hydrogen and C C- aliphatic and aromatic hydrocarbon radicals (and derivatives thereof containing relatively inertfunctional substituents) and at least one of the substituent groups, R R and R is a hydrocarbon radical. In the case of acid amides in which the R group is small, theamides are water-soluble and it is necessary to include about 5 to 15% by weight of the silica of a polyalkylene glycol waterproofing agent, such as UCON LB 550 X, a polyalkylene glycol produced by reaction of butanol and 1,2-propylene oxide of high molecular weight (e.g., about 1400). When the R groups are suifi ciently large, the acid amides are water-insoluble, as well as being oil-soluble, and function as waterproofing agents for the silica particles as well as dispersants therefor.

Examples of acid amides which are useful as dispersants for silica-thickened grease are: N-rnethyl formamide, N,N-dimethyl formamide, N,N-diethylform amide, N,N-dihexyl formamide, N,N-dihexadecyl formamide, N,N-diphenyl formamide, N,N-ditolyl formamide, N,N-dibenzyl formamide, N-butylacetamide, N-methyl acetamide, N,N-dimethyl acetamide, N,N-dibutyl acetamide, N,N-dioctyl acetamide, N-hexadecylacetamide, N- methyl lactamide, N,N-dimethyl lactamide, N-butyl-lactamide, N,N-dioctyl lactamide, N-methyl hexanamide, N,N-dimethyl hexanamide, N-butyl hexanamide, N,N-dibutyl hexanamide, N-phenyl hexanamide, N,N-diphenyl hexanamide, N-methyl benzamide, N,N-dirnethyl benzamide, N-butyl benzamide, N,N-diphenyl benzamide, N- methyl toluamide, N,N-dibutyl toluamide, N-phenyl toluamide, N,N-phenylmethyl toluamide, butyramide, hexanamide, octanamide, oetadecanamide, benzamide, toluamide, and N-octylbenzamide. These acid amides are generally operative as dispersants for silica thickened grease when added to the grease composition at a concentration of about 0.25 to 2.25% by weight of the grease.

In order to demonstrate the invention, several grease compositions were prepared to provide a comparison between the improved grease of this invention and other grease compositions.

EXAMPLE I A conventional grease-making kettle was charged with 91.2 parts by weight of vis. bright stock and 0.8 part by weight of N-methyl acetamide. The mixture was thoroughly agitated and heated to l90-215 F. To this mixture there was added 8.0 parts by weight of finely divided, amorphous silica. The silica used was Cab-O- Sil" silica which is produced by the high-temperature reaction of a siliceous material, e.g., high-temperature, vapor-phase hydrolysis of silicon tetrachloride. The agitation of the mixture was continued during addition of the silica gelling agent and the mixture was further agitated and maintained at -2l5 F. for a period of about 90 minutes. The grease thus produced was then charged to a colloid mill with a rotor-stator clearance The silica is' of 0.003", andzwasmilled at a flow rate of 0.6-0.7 pound per minute. The grease thus obtained was then allowed to cool and was tested using a standard cone-penetration test. The grease had an unworked penetration of 232 and a worked-penetration of 239, which is a ,,NLGI f#,3; grease. The narrow range between unworkedandworkedi penetrations is indicative of a highshear stability in this.

grease. This grease is limited to essentially anhydrous applications since it is decomposed by contact with large amounts of water. The grease, however, can be rendered stable to water byincorporation therein, during the initial agitation step, of a suitable waterproofing agent, such as Ucon LBSSOX (a polyethylene glycol waterproofingv agent, previously identified), in the'same amount as the acid amide. EXAMPLE, H

agitation of the mixture was continued during the addition of the silica, and the mixture was agitated and maintained at 190215 F. for a period of about 90 minutes. The grease was then charged to a colloid mill with a rotor-stator clearance of 0.003", and was milled at a flow rate of 0.6-0.7 pound per minute. The grease was then allowed to cool and was tested using a standard cone-penetration test. This grease had an unworked penetration of 251 and 21 Worked penetration of 263, corresponding to a #2 grease. The narrow range, of the worked and unworked penetration indicates a high shear stability for this grease. This grease also is limited in application to substantially anhydrousconditions unless a waterproofing agent (Ucon LB550X, in the same p ro portion as the N methyl lactamide) is used.. When the grease is waterprcofed, as just described, there is no appreciable change in yield or hardness.

EXAMPLE III In still another experiment a grease was compounded, using the procedure described in Examples I and II, from 90.08 parts by weight of 160 vis. bright stock, 0.92 part by weight of Ucon LBSSOX (apolyalkylene glycol produced by reaction of butanol and 1,2-propylene.

oxide and having an average molecularweiaht of about. 1400), and 9.0 parts by weight of Cab-O-Sil silica. The grease produced from these ingredients had an unworked penetration of 241 and. a worked penetration of 275, a #2 grease. The wide range between the .1111? worked and worked penetration in this grease, however, is indicative of: relatively poor shear stability. Further: more, the higher percentage of silicarequired for this grease is indicative of a much lower yield of the grease,- relative to the greases produced. in Examples I andII.

7 EXAMPLE IV Inseveral other experiments greases were compounded, using the procedure of Examples I and II, having the compositions and consistencies indicated in .Table I:

l Cah-O-Sil Silica.

2 Grease N o. 4N,N-dimethyl tormamide. Grease N o. -5 N-butyl acetamide. Grease No. 6N,N-dibutyl acetamide. Grease No.'7 \hexadoeyl ECElSETAiIIG. rease No. 8butyramide. Grease "N 0: 97 hexanam ids. Grease N o. 10N,N-diph enyl tormamide.

While therehave been described several preferred'embodiments of this invention, including several specific ex; amples of the best mode of carrying out this invention, it should be understood that within the scope of the appended claims this invention may be practiced otherwise than as specifically described.

What is claimed'is:

1. A lubricating grease consisting essentially of a major portion of a petroleumlubricating oil having in-.

corporated therein sufiicient finely divided silica to produce a gel-like grease structure and an oil-soluble acid amide of the formula whereR R and R are of the group consistingofhy drogen and C C hydrocarbon radicals-and at least.

oneof thesubstituents R R and R is a hydrocarbon radical, in an amount sufiicient to effect the complete dispersion of the silica.

2. A lubricating grease according to claim l-inwhichv the acid amide is present in the amount of.0.25 to 2.25 by weight of the grease.

3. A lubricating grease according to claim 1 in which the silica used in an amorphous silica of very fine particle size produced by the high-temperature, vapor-phase reaction of a siliceous material.

4. A lubricating grease according to claim '1 which additionally includes 5 to 15% by weight of the silica of a waterproofing agent for the silica.

5. A lubricating grease according to claim 1 in which theiacid amide is of the group consisting of N-substituted formamides, N-substituted acetamides, N-substituted lactamides, butyramide., and hexanamide.

6. A lubricating grease according to claim 4 in which the waterproofingagent is a polyoxyethylene glycol.

7. A lubricating grease consisting essentially of a major portion of a petroleum lubricating oil having incorporated therein 5-20% by weight of an amorphous silica of very fine particle size, produced by high-temperature reaction of a siliceous compound, and 0.25 to 2.25% by weight of the grease of a dispersing agent for the silica consisting of an oil-soluble hydrocarbon-substituted acid amide of the formula where R R and R are of the group consisting ofhy! drogen and C .C hydrocarbon radicals and at least one ofthesubstituentsR R and R is a hydrocarbon radiw cal.

8. A lubricatinggrease according to claim 7 which additionally includes 5-15 by weight of the silica of.

a polyoxyethylene glycol waterproofing. agent for. the

silica.

' 9. A lubricating grease according to claim 7 in which the acid amide is an N-substituted formamide.

10. A lubricating grease'according to claim 7 in which the, acid amide is an N-substituted acetamide.

11. A lubricating grease according to claim 7 in which the acid amide is anN-substituted lactamide.

12. A lubricating grease according to claim 7 in which 16. A .lubricating grease according to claim 7 in which the acid amide is N,N'-dimethyl formamide.

17. A lubricating grease according to claim 7in which the acid. amide .is N,N -di ph e nyl formamide,

References Cited in the file of this patent UNITED STATES PATENTS Sommer Apr. 21, 1953 Harman June 2, 1953 Braendle May 22, 1956 Marshall Oct. 9, 1956 

1. A LUBRICATING GREASE CONSISTING ESSENTIALLY OF A MAJOR PORTION OF A PETROLEUM LUBRICATING OIL HAVING INCORPORATED THEREIN SUFFICIENT FINELY DIVIDED SILICA TO PRODUCE A GEL-LIKE GREASE STRUCTURE AND AN OIL-SOLUBLE ACID AMIDE OF THE FORMULA 